Circuit stabilizer



DeC- 4, 1951 R. M. wlLMoTTE l-:rAL 2,577,668

CIRCUIT STABILIZER Filed May 15, 1944 4 Sheets-Sheet 1 L Rel/ml' De- 4, 1951 R. M. wlLMoTTE ETAL 2,577,658

CIRCUIT STABILIZER Filed May 15, 1944 4 Sheets-Sheet 2 Cl A] Az DI A! CZ n Az oU/TPuT oF TUBE V/ OUTPUT of T055 V2 F/G Za V M DeC- 4, 1951 R. M. wlLMoTTE ETAL. 2,577,668

' CIRCUIT STABILIZER Filed May 1'5, 1944 4 Silleets-Sheecl 4 To Commuaar:

Patented Dec. 4, 1951 UNITED STATES PATENT FFME] CIRCUIT STABILIZER of Delaware Application May 15, 1944, Serial No. 535,787

16 Claims. 1

This invention relates to means for automatically maintaining predetermined phase and amplitude relations among a plurality of currents. It is necessary in many systems to maintain the impedance of component circuits constant. In antenna arrays, for example, it is essential that there be no departures of the phases or amplitudes of the several antenna currents, since such departures would cause deformations of the radiation pattern of the array. Difficulty in maintaining a desired radiation pattern has been experienced in the past because of variations of the impedance of the antennas and circuits caused by weather changes and other factors.

It is an object of this invention to provide a system for automatically controlling the phase or amplitude, or both, of the current in a network. It is another object of this invention to maintain the impedance of a network constant. It is a further object of this invention to providea system of the kind herein referred to which shall be substantially independent of tube ageing and other variations in the control circuits. It is a s further object of this invention to providea stabilized antenna which will automatically maintain a predetermined radiation pattern. It is another object of the invention to provide a self -stabilizing electron tube commutator. It is another object ofthis invention to provide means for monitoring the phases and amplitudes of the currents in an antenna array or other system of networks. It is a still further object of this invention to provide a phase comparison system for operating a differential relay which shall be independent of incidental amplitude variations occurring in the system.

The invention will be more fully understood from the following detailed description and accompanying drawings. in which:

Figure 1 shows the phase responsive portion of the system applied to an antenna array,

VFigures 1a through le. inclusive. are diagrams indicating the operation of the commutator circuit,

Figure 2 shows a mechanical commutator,

Figures 2a and 2b are diagrams illustrating the operation of another part of the system;I

lllgure 2c is a diagram pertaining to the operation of the mechanical commutator,

(Cl. 343-101),l

Figures 6 and '7 are vector diagrams of ,the operation of the system shown in Figure. 5..

Reference is now mfade to Figure 1 showing the portion of the systeni for maintaining predetermined phase relationships among a plurality of alternating currents or voltages of the s..me frefluency. Thev currents whose phases are monltored may be those in a broadcast antenna system. In practice the antenna array may include two ormore radiators. Three such radiators are shown in Figure l and are designated by the referencenumerals I, 2. and 3.. The voltages derived from. radiators i and 2 by coupling loops e and 4', or anyother means. are impressed on input circuits of electron tubes VI and V2. Similar voltages derived from other pairs of radiators of the antenna array mfay be impressed on similar electron tube circuits not shown. The voltage B, derived from loop Il is impressed cophasally on the leads Ll and L2. The voltage, A, derived from loop l is fed through transformer I counterphasally to the leads LI and L2. The phase shifting circuit 5 is adjusted so that the voltages A andB are impressed on the leads LI and L2 in phase quadrature.

Theplate circuits of tubes VI and V2 are energizeciby-- an A. C. power source, 8. which may be 60 C. P. S. or any other convenient frequency, supplied through transformer 9. A load impedance It common to the pl'ate circuits of tubes Vi and V2 is connected between a center tap of the secondary of transformer 9 and a tap on resistor I l. The plates of tubes Vl and V2 are connected to ground through radio frequency bypass condensers l2 and I3. The tap on resistor Il is set so that no 60 cycle component from the power source, t, appears across impedance IB when the voltages from pickup loops and t are applied to the input circuit 'of tubes VI and V2 in phase quadrature.

The operation of the system of Figure 1 may be best understood by. reference to Figures la, 1b.' lc, ld, and le. The vector Al in Figure 1a represents the voltage impressed by transformer l on the control grid of tube VI; the vector B represents the voltage across resistor 6 impressed on the control grids of tubes VI and V2 through the transformer 1; 'and A2 represents the voltage impressed by transformer 'l on the control Figure 3 shows the amplitude :expansive 4pm'- 30 grid of tube V2. The resultant voltages 0n the tion of the system,

Figure 4 shows a modification of shown in Figures l and 3.

Figure 5 schematically shows another modification of the invention, and.

the system control grids of tubes VI and V2 are, therefore, represented by CI and C2, respectively. As long as the voltages A and B are in phase quadrature the resultants Cl and C2 are equal. The voltage across load impedance I9 would. in this case, be

as shown in Figure lc. It can be seen that this output voltage has no 60 cycle component. However, when the phase of the current in antenna 2 drift with respect to the current in antenna I, a voltage BI. Figure lb, would be impressed on the control grids and the resultant voltages on the control grids of tubes VI and V2 would be as represented by vectors DI and D2, respectively,

as is shown in Figure 1b. The voltage DI is now larger thanA D2, the signals applied to the control grids of tubes VI and V2 are no longer equal and the output of the commutator appearing across the impedance Il contains a 60 cycle component as indicated in Figure 1d. AIi' the phase of the current in antenna 2 should drift in the opppsitedirection. the output of the commutator would then be as indicated in Figure 1e. It will be seen from inspection of Figures 1d and le, that the the electron tube commutator of Figure l. Corresponding to the sine wave envelope of Figure 1d, for example, the mechanical commutator will ,have an output whose envelope consists of substantially rectangular pulses such as shown in vFigure 2c. The output from lead Ll to amplifier I4, will be the pulses labeled MI, and the output from lead L2 will be the pulses labeled M2. In ,this figure only the upper halves of the pulses fare shown. It can be seen in Figure 2c that the ,envelope of the pulses M I and M2 has a 60 cycle component.

l The output voltages of the commutator are amplified by an\R. F. amplifier I4 and demodulated by detector I5. The 60 cycle component is then isolated by filter I5 amplified in amplifier I1 and impressed co-phasally on the' control grid of tubes V3 and V4. A 60 cycle voltage is also im- 'pre'ssed by the supply source 3 through a trans- 4former I3 on a pair of diodes V5 and V6.5 The .outputs of the diodes develop alternate negative j pulses across the load resistors2ll and 2l, which are applied to the control grids of tubes V3 and .V4. respectively. A suitable fixed or self bias 22 may be applied to the control grids of tubes V3 and V4. The voltages on the control grids of .tubes V3 4and V4 are indicated in Figures 2a and l2b. respectively. These ilgures illustrate the case represented by Figure 1d or Figure 2c. "It will be lnoted that'the grid voltage of tube V3 swings above cutoi! during each half cycle and that tube V3 will therefore pass platel current, while the grid voltage on tube V4 remains below cuto as indicated by curve S in Figure 2b and hence tube V4 will draw no plate current. When the situation illustrated in Figure le prevails, it is evident ltube V4 will then pass plate current but tube V3 will not pass plate current. When the antenna 'currents have their right predetermined phases ,and hence appear in phase quadrature on the grids of tubes VI and V2, only the negative pulses developed by diodes V5 and V6 will be impressed lo n the grids of V3 and V4 and neither of these tubes will then pass plate current. It is appar- 'e'nt then that relay 23 will operate if the phase of the current in antenna 2. advances with respect to its predetermined position, and relay 24 4 will be operated if the phase of the current in antenna 2 lags behind its predetermined posiion.

Relays 23 and 24 are shown. connected to any suitable reversible motor 3|, in series with an A. C. power source.' These relays may be electronic or magnetic types. Closing of relay 23 in response to an output from tube V3 causes the motor to rotate in one direction and the closing of relay 24 in response to an output from tube V4 causes the motor to rotate in the opposite direction. The motor is mechanically coupled to the input series elements 32 of a T network, which element affects chiefly the phase shift through the network, the coupling being such that element 32 will be adjusted to return the phase of the current in antenna 2 to its predetermined position whenever a deviation therefrom occurs. Condenser 23 and 21 are shunted across relays 23 and 24 to prevent chattering of the relays.

By means of networks similar to those shown in Figure 1 the relative phases of the current in each of the other radiators of the array with respect toradiator I. maybe controlled in the same manner as the phase of the current in antenna 2. Thus in a second system similar to that shown in Figure l, loop 4" would replace loop 4', and the voltages derived from loops 4 and 4" would be utilized in the same manner as the voltages from circuits A and B in Figure l, to control the relative phase of current in radiator 3 with respect to the phase of the -current in radiator I.

In order to measure the phase relations of the antenna currents a zero-centered voltmeter 25 is connected across the plates of tubes V3 and V4. The meter is calibrated so'that it reads the magnitude and direction of phase deviations.

while a circuit designated byW impresses an'R. F.

voltage on resistor 4I. The center tap of resistors 4I and 42 is grounded and the ungrounded ends of the resistors 4I and 42 are connected by the leads LI and L2 to the commutator\43, similarly to Figures l and 2. Aside from the input resistors 4I, 42, the commutator 43 may be the same as the one shown in Figure 1 or Figure 2.

R.. F. amplifier 44, detector 45, filter 46, amplifier 41, and relay control circuit 48 perform essentially the same functions and maybe similar to their counterparts in Figure 1, and hence are represented'by a block diagram. The relays 43 and 53 correspond to the relays 23 and .24 of Figure l and control the reversible motor 55. The motor is mechanically coupled to the adjustable element 34 of the T network in the R. F. feeder for antenna 2. Adjustment of element 34 varies mainly the amplitude of the current in antenna 2. The

motor 55 is coupled to element 34 so that the latter is varied to re-establish the predetermined ratio of the current amplitudes whenever a deviation therefrom occurs.

The circuits V and W are adjusted soas to impress voltages of the same magnitudes on resistors 4I' and 42 when the antenna currents have their predetermined amplitude ratio. It is evident that under this condition the commutator output will 14 not have a 60 cycle component and the relays 4I termined current ratio.

and 50 and motor 53 will remain unenerglzed. VIf

cycle component and relay 49 or 50 would close and motor 55 would operate to adjust element 34 of the T network so as to re-establish the-prede- A zero-centered voltmeter I is connected across the plates of the relay control tubes 48 in the same manner as meter 25 in Figure l. This meter 5I indicates the amount and direction of relative changes of amplitude of antenna current.

Figure 4 shows an alternative method and means for obtaining the voltages which are applied to the commutators, for both phase and amplitude control. The antenna 2. for example, is shown connected to an R. F. feeder which includes the elements 32, 33, and 34, of the T network. The primary winding of a transformer 88 is placed in series with the R. F. feeder connected to the T network and a condenser potentiometer 3I, 62 is connected across the input of the T network. The transformer 63 impresses voltages on the inputs of the phase and amplitude comparing commutators through circuit W and the condenser potentiometer impresses voltages 0n the commutatorinputs through circuit V. It will be understood, of course, that a similar transformer and potentiometer would be used in R. F. feeders to each of the other antennas, except pos-v sibly reference antenna I. It is evident-that a change in the phase or amplitude of the antenna current would cause a corresponding change in the phase or magnitude of the voltage in circuit W with respect to the voltage in circuit V. These voltages may, then, be utilized in the same manner as they are in Figure 1 to operate reversible motors 3i and 55 to control the resistive and rea change in the relatin between vector B and` i `.agarra vector A which isequal to a vector Q.

A voltage proportional to voltage A and a 'voltage proportional to voltage B are picked out and are combined in a circuit BI with amplitudes such as to produce aresultant PI substantially in quadrature with vector Q and equal in amplitude to l voltage A. The amplitude of this voltage PI active components of the impedance network,

which is shown as a simple T network, but in practice may include elements other than or ad- Ilitional to elements 32, 33, and 34.

The application of the control system described above is not limited to networks containing one element whose adjustment, over a limited range,

affects only the resistive component and another element whose adjustment affects only the reactive component. If a re-adjustment of ele- `ment 32, for example, should also cause the resistive component of the network to change, the system would automatically operate to vary element 34 to compensate for this incidental change of the resistive component. The system will come to rest onh' when the initial impedance of the network has been reestablished.

This interlocking of the control of elements 32 and 34 may be substantially eliminated, however, by the following scheme, a diagram of which is shown in Figure 5. Let us suppose two voltages. A and B, are again, as in Figures 1 and 3. to be retained in the same phase and amplitude relationship. A voltage B is derived from a line connected to a R. F. source through two variable impedances ZI' and Z2. These impedances may be the elements 32 and 34 of Figures 1 and 3 or other impedances. Likewise, a voltage A is derived from a line connected to the R. F. source through any impedance Z.

When ZI' is varied slightly voltage B is altered relatively to voltage A by a vector P, Figure. 6, the vector P being measured by a combination .of the change in the amplitude 'and phase of vector B relative to vector A; Similarly, a small change in the variable impedance Z2 -produces is then balanced against the amplitude of voltage A across resistor 63. An unbalanced voltage across resistor B3 operates a motor 6l controlling impedance ZI, -tending to bring back the balanced condition.` Under those conditions a small change in impedance Z2 will have little eifect on the voltage PI that controls the motor 61 operating the impedance ZI. The motor 67 and 38 are controlled by circuits 6E and 63 which are the same as those of Figures l and 3. By following a similar procedure we adjust the circuit controlling motor'SB which operates the variable impedance Z2 so that a small change l'n ZI will have little eiect on the voltage that controis the motor 68 operating the variable impedance Z2. Under those conditions the-impedances ZI and Z2 will be substantially independent variables.

The procedure for designing the controlling circuits is: First determine the phase of the vector P by mak-ing a small change in ZI, and the phase ofthe vector Q by making a small change in Z2. Second, calculate the phase shift necessary in voltage B relative to voltage A in order to obtain a resultant PI of the combination of A and B which lain-quadrature to Q (in order to operate the motor controlling ZI) and QI in quadrature to P (in order to operate the motor controlling Z2) Y According to the `procedure outlined, the phase relationship between the vectors P and Q may theoretically be any value except exactly in phase or out of phase. Preferably, however, their phase relationship is in quadrature. Although,

for' the sake of deniteness, the A. C. source 8 has been indicated as being 60 C. P. S., other frequencies may-be used.

Another method of -combining a voltage B developedin a circuit with a reference voltage A tocontrol an impedance ZI of that circuit independently of an impedance Z2 of the circuit will now be described with reference to Figures 5 and 7. The circuit may be the T network shown in Figures 1 and 3 and impedances Zi and VZ2 may be the elements 32 and 34 of such a network. `Suppose (see Figure 7) a small change is made in Z2 and it is found that the output voltage of the circuit, represented, by vector B, undergoes a change represented by the vector Q. Then the phase of voltage B is shifted so that Q is in phase quadrature with A. 'We then tap off voltages AI and A2 from the circuit containing voltage A and combine these voltages with B to obtain the resultant voltages VI and V2. These voltages are then applied to circuits 65 and 63 in the manner shown in Figure 5. Since these voltages VI and V2 do not change their relative amplitudes with a small change of Z2, the output of the circuit of Figure 5 can be used to control ZI in response only to variations of ZI. By a similar procedure we may make the control of Z2 substantially independent variations of ZI.

An important-feature of this invention is that the operation of the control circuits is independent of the gain of all tubes following the commutator.- and since the commutator either matas has n'o tabe'sor isa cathode :answer circuit it is practically unan'ected by the tube variations. Thus. a( high degree of reliability is attained. It has been found thatthe reliability'of' the system is-enhanced when the plate voltages of tube'sfVi and V2 are reduced to 25 or 30 volts. 1 if; While the several figures of the drawings-show specific embodiments and. adaptations o! this invention, --it is to be understood that the principles and circuits disclosedherein may beaplplied to systems different from 'those illustrated without departing from thespirit'and scope of the' invention as defined inthe claims. -We claim: a 1 "TL 'I'n combination, a pair of electron tubes each having an anode, cathode and control grid, means for impressing potentials of a. iirstfrequency counterphasaliy on the control fgrids, m'eans for impressing potentials-of the samefreqency and normally inphase quadrature with said first potentials cophasally on said control grids, a load impedance connected between the cathodes and ground, a low impedanceconnection-for said first frequency from each' anode y 4to ground, means for impressing a voltagesof a second frequency counterphasally between' fthe anod'es and ground, the control grids being connected to theicathodes through the load impedance, means for balancing out the. see'ond frequency voltage across the load .impedance when the ilrst frequency potentials are in phase quadrature, -whereby the second frequency voltage ,across'the load impedance has a given phase xwhen thee-phase difference between the rst frequency vpotentials is less than 90 degrees and an lopposite phase when-the -phase difference is more than 90 degrees.

2'. In combination, a pair of electron tubes each -having an anode, cathode and control grid,

means for impressing normally equal potentials fof a first frequency on the control grids, a load ,impedance connected between the cathodes. and

ground, a low impedance connection for said first frequency from each anode to ground, means for impressing a voltage of a second frequency ';ouriterphasally between the anodes and ground, the'control grids being connected to the cathodes through the load impedance, means for balancing -out the second frequency voltage across the load v'impedance when the first frequency potentials "are of same magnitude, whereby the second ire- 'fquency voltage'across the load 'impedance has. a .given phase when the potentials on one of .the

control grids has a greater magnitude than the -potentials on the other control 'grid and an opposite phase when the 'potentials on the one Agrid have a lesser magnitude than the potentials on the other grid. 4

3. The combination set forth in claim l including means responsive tothe phase of the second frequency voltage across the lo'ad impedance 'for reducing relative phase shifts of said -rrst frequency potentials, and the voltage between the anodes and ground being of the order-of :25l volts.

4. lThe combination set forth in claimA 2 in-7 c luding means vresponsive 'to vthe phase of the second frequency voltage across the -load' impedance for reducingvrelative shifts in magnitude of said 'first frequency potentials.

" 5. The combination set forth in cl'aim'l' including means for measuring the relative phases of said first frequency'potentialsm 'f 6. The combination set-forth in claim 2 indetermined relationship of both amplitude and phaseoi current fiow to said plurality of radiators to maintain a predetermined entire contourof radiation pattern generated by said plurality of radiators, separate 'means coupled intermediate said transmitter and at least certain of said radiators. and responslveto deviation from said predetermined relationship lof relative amplitudes and phases of individual current ow in said at least certain of said radiators with respect to currentin one of said radiators for re-establishing saidpredetermined relationship.

I'iitvln a system for controlling the relative amplitudes and phases of currents in a pair of radiators, a transmitter coupled-to said radiators', s .phase .and amplitude controlsystem in circuit between said transmitter and one of said radiators, said system comprising iirst means for varyin'g substantially only amplitude of current fiow tofsa'id4 radiators vand second means forvarying 'substantially only phase of said current-now to said one of said radiators, means for measuring relative amplitudes of current flow to said pair of radiators, means responsive to said last mentioned means for actuating said first means tore-esteblish a predetermined amplitude relation between .current now in said pair of radiators upon devia'.-

tion from said predetermined amplitude relation,-

meansfor measuring relative phase of current flow inv-said pair -of radiators, means responsive .fto said last mentioned means for actuating -said second means to establish a predetermined phase Arelation'between currents in said pair ,of radiators upon -deviation from saidlpredetermined phase Irelation. l, l u, .I 9. In a system for controlling the relative amplitudes and phase of currents in at least three radiators, wherein. amplitude and phase of current -a first of said radiators is established as .s tandard, first means for measuring the ratios between .the amplitudes of current in said first fofisaid radiators and in the remainder of said Vradiators taken individually, second means for measuring ',he differences in the phases of the cur.- rents'in'ysaid first of said radiators and in there mainder of' said radiators .taken individually. means responsive to said first means for controlling 'primarily' the amplitudes .of currents vin .,the'remainder of said radiators to maintain said f'relative amplitudes constant, and means responsive to said second means for maintainingprimarily said relative phases constant'. l

l0. Ina system for controlling the relative lphases' and amplitudes of two currents, first means for varying substantially only the phase of 'one of said currents, second means for varying substantially only the amplitude of said one of .said currents, third means for generating a first 'c'ontrol signal having a sense determined by sens'e fof' deviation of said relative amplitudes from a .predetermined ratio. fourth means for generating ja 'further control signal having a sense determined -by sense of deviation of said relative phases "from a predetermined relation, means responsive lto said first control signall forl controlling said second means to reduce said deviation of said relfativevamplitudes from said predetermined ratio, means responsive to said further control signal for controlling said first means to 'reduce said l' deviation of saidrelative phases from saidpregermes 11. An antenna array comprising, a plurality of radiators, a transmitter coupled via a separate channel to each of said radiators, a separate circuit means for measuring the phase of the current in each of said radiators with respect to a predetermined phase, and means responsive to deviation of the phase of the current in each one of said radiators from a value predetermined for that radiator for re-establishing said value to minimize changes in the antenna radiation pattern provided by said array.

12. In combination, a pair of spatially separated radiators, a source of high frequency current for said radiators, means for deriving a signal proportional in amplitude to the amplitude of current in one of said radiators, means for deriving a signal proportional in amplitude to the amplitude of current in the other of said radiators, means responsive to deviation of the ratio of amplitudes of said signals from a predetermined ratio for generating a control signal representative of said deviation, means for controlling amplitude of current ow in said one of said radiators, and means responsive to said control signals for actuating said means for controlling amplitude of current ow in said one of said radiators to re-establish said ratio.

13. In combination, a pair of spatially separated radiators, a source of high frequency current for said radiators, means for deriving a iirst control signal in response to deviation of relative phase of currents in said pair of radiators from a predetermined value, means for deriving a second signal proportional in amplitude to the amplitude of current in one of said radiators, means for deriving a further signal proportional in amplitude to the amplitude of current in the other of said radiators, means responsive to the deviation of the ratio of amplitudes of said second and further signals from a predetermined ratio for generating another control signal representative of said deviation of the ratio of amplitudes, means for controlling the relative phase of said currents in said pair of radiators and for controlling amplitude of current in said one of said radiators only, and means responsive to said first control signal and said another control signal for actuating said means for controlling amplitude of current ow in said one of said radiators and relative phase of said currents in f said pair of radiators to re-establish said predetermined relative phase and said ratio of amplltudes.

14. An antenna array comprising three radiators, a transmitter coupled via a separate channel to each of said three radiators, means comprising said transmitter for establishing in each of two of said three radiators currents having a predetermined phase relation to the current in the remaining radiator, said last means comprising means responsive to deviations of relative phase oi' currents in each of said two of said three radiators from said predetermined phase relation to re-establish said predetermined phase relation for each of said two of said three radiators.

15. An antenna array comprising three radiators, a transmitter coupled via a separate channel to each of said three radiators, means for deriving signals proportional in amplitude to the amplitude of current in each of said three radiators, means responsive to deviations of the ratios of amplitudes of each of two of said signals taken with the remaining one of said signals from a predetermined ratio for each of said two of said signals for generating control signals representative of said deviations, means for controlling amplitude of said current in selected ones of said three radiators, and means responsive to said control signals for actuating said means for controlling amplitude of current in said selected one of said three radiators to re-establish said ratio for each of said two of said control signals.

16. An antenna array comprising three radiators, means comprising a transmitter coupled via a separate channel to each of said three radiators, means comprising said transmitter for establishing in two of said three radiators currents having a predetermined phase relation to the current in the remaining radiator, means for deriving iirst control signals in response to deviation of the phase of said currents in said two of said three radiators from said predetermined phase relation, means for deriving signals proportional in amplitude to the amplitudes of currents in each of said three radiators, means responsive to deviations of the ratio of amplitudes of each of two of said signals, taken with the remaining one of said signals, from a ratio predetermined for each of said two of said signals, for generating second control signals representative of said deviations, means responsive to said first control signals and to said second control signals for restoring said predetermined phase relations and amplitude ratios.

RAYMOND M. WILMOTTE. CLEMENS X. CASTLE.

7 ille of this patent:

UNITED STATES PATENTS Number Name Date 1,643,323 Stone Sept. 27, 1927 2,042,831 Crosby June 2, 1936 2,080,081 -Lothe et al. May 11, 1937 2,173,858 Pierce et al. Sept. 26, 1939 2,175,017 Cockrell Oct. 3, 1939 2,190,037 Neufeld Feb. 13, 1940 2,286,839 Schelkunoi June 16, 1942 2,398,335 Theis et al. Apr. 9, 1946 2,449,174 OBrien Sept. 14, 1948 FOREIGN PATENTS Number Country Date 735,055 France Aug. 13, 1932 458,734 Great Britain Dec. 24, 1936 503,471 Great Britain Apr. 6, 1939 

